Optical coupling unit and method for inserting optical wave guides into an optical coupling unit

ABSTRACT

The invention relates to a coupling unit for optically coupling a multi-channel optical plug-in element to at least one opto-electronic converter of a multi-channel transmitter and/or receiver unit and to a method for inserting optical wave guides into said optical coupling unit. The coupling unit comprises a first coupling side for optical coupling to the multi-channel optical plug-in element, a second coupling side for optical coupling to the at least one opto-electronic converter and a plurality of receiving openings for optical wave guides; said openings being arranged on a plane, extending from the first coupling side to the second coupling side. According to the invention, the coupling unit is embodied in a single piece and the receiving openings extend at least partially inside the coupling unit. The optical wave guides are inserted into the single-piece coupling unit with the aid of an optical plug-in element. The receiving openings of the optical plug-in element are flush with the receiving elements of the coupling unit.

[0001] The invention relates to a coupling unit for optically coupling amulti-channel optical plug-in element to at least one opto-electronicconverter of a multi-channel transmitting and/or receiving unit, and toa method for inserting optical waveguides into a coupling unit of thistype.

[0002] To couple and connect an optical plug-in element, in particularan optical connector, to light-emitting or light-receivingopto-electronic converters, it is known to provide a separate opticalcoupling unit. In this case, the high-frequency optical signals whichare to be transmitted are conducted and guided from the opticalconnector to the opto-electronic converters and in the oppositedirection via the optical coupling unit.

[0003] Conventional coupling units of this type comprise a two-partsupport part in which optical waveguides (glass fibers) arranged in aplane are held in V-shaped grooves of the one part. The opticalwaveguides are pressed into the grooves by an additional slide, which isprovided by the other part. The end surfaces are then polished and guidepins fitted.

[0004] The known coupling unit has the disadvantage that the adaptationand fixing of the glass fibers by means of a slide can be achieved onlyby all of the dimensions having the highest possible accuracy, thisbeing associated with a high outlay and a high reject rate. Also,acceptable positional tolerances between the V-shaped grooves for theoptical waveguides and bores for guide pins, which bores are arranged atthe side of the V-shaped grooves, can be achieved only with difficulty.High injection molding costs arise due to complicated measurements,tests and adaptations.

[0005] A further disadvantage resides in the fact that the guide pinsrequired are relatively expensive pins with an annular projection, thepins being placed into bores for the guide pins with a shaped undercut.Overall, assembly of the known coupling unit, which requires a highoutlay on fabrication, is therefore relatively complicated.

[0006] Starting from this prior art, the present invention is based onthe object of providing an optical coupling unit and a method forinserting optical waveguides into an optical coupling unit of this type,said coupling unit and method making it possible to produce the couplingunit and insert optical waveguides into the coupling unit in a simplemanner.

[0007] This object is achieved according to the invention by a couplingunit having the features of claim 1 and a method having the features ofclaim 12. Preferred and advantageous refinements of the invention arespecified in the subclaims.

[0008] Accordingly, provision is made for the coupling unit to be ofsingle-piece design, the receiving openings for optical waveguides whichare to be introduced into the coupling unit extending at least partiallyin the interior of the coupling unit. Just a single part is thereforeused according to the invention as the coupling unit. In this part areformed the receiving openings for the optical waveguides andlongitudinal bores for receiving and positioning guide pins with whichthe coupling unit can be aligned in a defined manner with respect toother elements, in particular an optical connector.

[0009] Production of the coupling unit as one part means that all of theproblems which are associated in the prior art with the use of a slidefor inserting the optical waveguides no longer apply. In particular,force-controlled assembly is not necessary and the problem of applyinguneven pressure to the optical waveguides does not exist. In order toput the optical waveguides in place, the latter are instead insertedinto the corresponding receiving openings of the coupling unit, asdescribed further below. There is advantageously also a reduced numberof components, so that two injection molds are not required in order toproduce the coupling unit.

[0010] A further advantage of the solution according to the inventionresides in the fact that the receiving openings for the opticalwaveguides are surrounded on all sides by identical materialthicknesses, so that a compact, closed and protected arrangement isprovided.

[0011] In one preferred refinement of the invention, the coupling unithas, on its upper or lower side, a cutout which is preferably arrangedcentrally and partially exposes the receiving openings for the opticalwaveguides. It is possible to place an adhesive for bonding the opticalwaveguides in the receiving openings into the coupling unit via thecutout.

[0012] In one preferred development, the coupling unit is assigned anadditional auxiliary part having a knob protruding from an essentiallyplanar surface. In this case, the coupling unit can be arranged on theauxiliary part in such a manner that the knob projects into the cutoutof the coupling unit and comes to rest adjacent to the receivingopenings for the optical waveguides. The additional auxiliary partserves as an insertion aid and holds down the optical waveguides in theregion of the cutout when the latter are being inserted.

[0013] The coupling unit preferably has means for receiving and latchingguide pins (also referred to as centering pins). These areadvantageously two longitudinal bores which extend in each case at theside of the receiving openings for the optical waveguides and have aconstriction which serves in each case for the latching of a guide pin.The associated guide pin is preferably provided here with an annulargroove which latches in an interlocking manner into the constriction ofthe longitudinal bore.

[0014] In comparison with the previous use of guide pins havingthickened sections, the use of guide pins having an annular groove hasthe advantage of a simpler and more cost-effective method of production.The guide pins are thus preferably produced by means of centerlesscircular grinding machines, the guide pin being moved axially betweentwo disks rotating in opposite directions. This method also has theadvantage of enabling guide pins to be produced with little surfaceroughness. If the guide pins have a smooth surface, the wear on thecoupling partner is advantageously reduced.

[0015] In one preferred refinement of the invention, the first couplingside of the coupling unit has the same basic dimensions as the opticalplug-in element to be coupled, with, in particular, receiving openingsof the optical plug-in element being aligned with the receiving openingsfor the optical waveguides of the coupling unit. This permits a simpleinsertion process when placing the optical waveguides into the couplingunit: the optical plug-in element serves as an insertion aid forlocating the small, high-precision receiving openings on the firstcoupling side of the coupling element.

[0016] The second coupling side of the coupling unit preferably has abeveled projection exposing the receiving openings. In this case, a beamdeflection between the optical waveguides and associated, opticallyactive surfaces of the opto-electronic converter takes place viacoupling-side end surfaces of optical waveguides which are placed intothe receiving openings.

[0017] The optical coupling unit preferably consists of the samematerial as the optical plug-in element to be coupled. In particular,the optical coupling unit consists of the same material as thewaveguide-supporting, optical fiber end piece of the plug-in element(referred to in general as “ferrule”). By adapting the material, anidentical coefficient of expansion is provided in the event oftemperature changes, so that the quality of the coupling between thecoupling unit and optical plug-in element is not affected by temperaturechanges.

[0018] The receiving openings in the coupling unit for the opticalwaveguides are preferably designed as high-precision bores. In thiscase, provision may be made for the bores to be of circular design incross section.

[0019] The method according to the invention is distinguished by thefollowing steps:

[0020] a) providing a multi-channel optical plug-in element havingreceiving openings for optical waveguides, said openings being arrangedin a plane,

[0021] b) arranging the multi-channel optical plug-in element on thefirst coupling side of the coupling unit in such a manner that thereceiving openings of the optical connector element are aligned with thereceiving openings of the coupling unit,

[0022] c) inserting at least one optical waveguide initially into theoptical plug-in element and continuing into the coupling unit, and

[0023] d) bonding the optical waveguides in the receiving openings ofthe coupling unit.

[0024] The coupling unit preferably has a cutout in which to placeadhesive and is placed during the insertion process onto an additionalauxiliary part having a protruding knob in such a manner that thewaveguides to be inserted are prevented by the protruding knob fromleaving the receiving openings in the region of the cutout. In thiscase, the auxiliary part provides a type of insertion aid which ensuresthat the insertion process takes place even in the region of the cutoutof the coupling unit and facilitates the fabrication of the glassfibers.

[0025] After the insertion process is completed, the optical waveguidesare beveled on the second coupling side of the coupling unit in such amanner that their end surfaces cause a beam deflection by 90° betweenthe optical waveguides and optically active zones of opto-electronicconverters of a transmitting and/or receiving unit.

[0026] A standard MT ferrule is preferably used as the multi-channeloptical plug-in element, since this enables existing parts andgeometries to be used. In principle, however, any desired opticalmulti-fiber connector or an auxiliary part analogous thereto can be usedas the optical plug-in element.

[0027] The invention will be explained in greater detail below using anumber of exemplary embodiments with reference to the figures of thedrawing, in which:

[0028]FIG. 1 shows a perspective view of a coupling unit according tothe invention;

[0029]FIG. 2a shows a different perspective illustration of the couplingunit of FIG. 1, in which guide pins have been introduced into thecoupling unit;

[0030]FIG. 2b shows a perspective illustration of the coupling unit ofFIG. 2a from the other side;

[0031]FIG. 3 shows a perspective illustration of a coupling unit, aninsertion aid, an optical connector and an optical cable before glassfibers are inserted into the coupling unit;

[0032]FIG. 4 shows the coupled together elements of FIG. 3 duringinsertion of the glass fibers;

[0033]FIG. 5 shows a sectional illustration of the arrangement of FIG.4, and

[0034]FIG. 6 shows a perspective illustration of an optical connector, acoupling unit and an array of optically electronic converters.

[0035]FIG. 1 shows an exemplary embodiment of a coupling unit 1 forconnecting and conducting high-frequency optical signals, which areguided in optical waveguides, between an optical plug-in connector andat least one opto-electronic converter and vice versa.

[0036] The coupling unit 1 consists of a single-piece shaped plasticbody which is produced, for example, by injection molding. The couplingunit has an upper side 1 a, a lower side 1 b, two lateral side surfaces1 c, 1 d and a first coupling side 1 e, which is on the left in FIG. 1,and a second coupling side if, which is on the right in FIG. 1. Asillustrated in FIG. 6, the first coupling side 1 e serves for couplingto an optical connector and the second coupling side if serves for theoptical coupling to opto-electronic converters of a transmitting and/orreceiving unit.

[0037] On the second coupling side if, the coupling unit forms a beveledprojection 20 exposing the receiving openings 2 while the first couplingside 1 e has been ground to give a flat surface.

[0038] A multiplicity of receiving openings 2, which are preferablydesigned as bores, extend in parallel in a plane in the coupling unit 1.The bores are produced, for example, during production of the couplingunit by thin wires placed into an injection molding die. Furthermore,the coupling unit 1 has longitudinal bores 3 into which, according toFIGS. 2a and 2 b, are introduced guide pins which serve to align thecoupling unit 1 and the receiving openings 2 and waveguides arrangedtherein with respect to an optical connector or another couplingpartner.

[0039] Extending vertically from the surface 1 a of the coupling unit 1in the direction of the bores 3 are two lateral cutouts 4 which have, attheir one end, with two edges 41 being formed, a tapered, narrowerregion 42 in which the wall of the cutout 4 has a type of thickenedsection 43 (cf. FIG. 2b). As can be seen in FIG. 2b, the guide pinswhich are to be introduced into the bores 3 each have an annular groove51 which, when the guide pins 5 are inserted from one coupling side,come after a certain introductory distance into abutment against thetapered region 42 having the thickened sections 43 of the verticalopenings 4, in which case that region of the guide pins 5 which isadjacent to the groove 51 comes into abutment in an interlocking mannerwith the edges 41 of the openings 4. During introduction of the guidepins 5, the thickened sections 43 are elastically compressed in theprocess until the annular groove 51 comes into abutment against thethickened sections 43. The guide pins 5 are thereby retained and fixedin the longitudinal bores 3.

[0040] In this case, provision may be made both for the verticalopenings 4 to extend from the upper side 1 aas far as the lower side 1 bor else to reach only from one side as far as the bore 3.

[0041] In FIG. 2a it can be seen that a central cutout 6 is provided onthe one side 1 b of the coupling unit 1 and serves, after opticalwaveguides have been introduced into the receiving openings 2, toreceive adhesive and thereby to firmly bond the optical waveguides inthe coupling unit 1. For this purpose, the cutout 6 reaches into theregion of the receiving openings 2 for the optical waveguides.

[0042]FIG. 3 shows the elements required for inserting a plurality ofoptical waveguides of an optical cable into a coupling unit 1. In thiscase, in addition to the optical cable 7 having a multiplicity ofoptical waveguides 71, the coupling unit 1 described in FIGS. 1 to 3 andalso an unused optical connector 8 and an insertion aid 9 designed as aseparate part are provided. The optical connector 8 is preferably astandard connector, for example a standard MT ferrule for receivingtwelve optical waveguides.

[0043] The coupling unit 8 has, in a manner known per se, a housing 81,two guide pins 82 guided in longitudinal bores, a rear sheet-metalholding element 83 for holding and fixing the guide pins 82, andreceiving openings 85 for receiving the optical waveguides 71 of theoptical cable 7. A cutout 84 for providing a bonding seal for the glassfibers 71 is also provided. However, in this case, this cutout 84 is notfilled with adhesive. The coupling unit 8 serves merely as an insertionaid for the coupling unit 1 and not for fastening the optical waveguides71.

[0044] The centering aid 9 has, on an upper, planar surface 91, aprotruding knob 92 which has an upper surface 92 a arranged parallel tothe surface 91, and two angled surfaces 92 b, 92 c which are inclined inthe direction of the surface 91.

[0045]FIGS. 4 and 5 illustrate the arrangement of elements of FIG. 3during the insertion of the glass fibers 71 into the optical connector 8and the coupling unit 1. In this case, the coupling unit 1 sits on theinsertion aid 9 in such a manner that the protruding knob 92 of theinsertion aid 9 engages in the cutout 6 of the coupling unit 1,specifically approximately as far as the bottom of the cutout of thecoupling unit.

[0046] The insertion process now proceeds in such a manner that theoptical connector 8 is first of all fastened to the first coupling side1 e of the coupling unit by means of the guide pins 5 and 82. Owing toidentical basic dimensions and by means of the precisely aligned guidepins, coupling takes place in such a manner that the receiving openings85 of the optical connector 8, which openings receive the opticalwaveguides 71, are aligned with the receiving openings 2 of the couplingunit 1.

[0047] It is pointed out that the guide pins 5, 82 may be arrangedeither on the optical connector 8 or on the coupling unit 1. However,they are preferably provided on the coupling unit 1 and are fastenedthere as described with reference to FIG. 2a. A secure latching is thusproduced by the coupling unit engaging in an interlocking manner in thegroove 51 of the guide pin 5. The guide pin 5 can be produced in asimple manner by means of a centerless circular grinding machine. Theguide pin 5 has a smooth surface, which reduces the wear of the couplingpartner.

[0048] According to FIGS. 4 and 5, the optical waveguides 71 are passedthrough the receiving openings 85 of the optical connector 8 and thenthrough the receiving openings 2 of the coupling unit 1. As can be seenfrom FIG. 5, the knob 92 engaging in the cutout 6 of the coupling unitensures that the optical waveguides 71, which are glass fibers, are helddown during the insertion process for the following openings.

[0049] After the optical waveguides 71 have been inserted, adhesive ispoured into the cutout 6 of the coupling unit 1, with the opticalwaveguides being fixed in place. The optical connector 8 is now removed(for example after severing the optical waveguides) and the end orcoupling surfaces 1 e, if of the coupling unit 1 are polished. The guidepins are then fitted as described in respect of FIG. 2b if this has notyet taken place.

[0050]FIG. 6 shows all of the essential elements of an arrangement witha finished coupling unit. An optical connector 8 is coupled on the firstcoupling side 1 e of the coupling unit 1. It is pointed out here thatthe optical connector 8 is, unlike in FIGS. 3 to 5, a completelyfinished connector with optical waveguides placed in it and a polishedend surface. The optical connector 8 and the coupling unit 1 consist ofthe same material, so that there are identical coefficients of expansionif there is a change in temperature, and therefore improved couplingconditions. A receiving and transmitting unit 10 which has an array ofoptically electronic converters 11 is illustrated on the other couplingside if. Said converters are fitted on a customary support 12 andconnected electrically by means of a bonding process to a printedcircuit board (not illustrated). The obliquely ground and polished endsurfaces 71 a of the glass fibers 71 cause the optical signals to bedeflected in a manner known per se by 90° and thus to strike against therespectively assigned converters 11. An arrangement of this type isdescribed, for example, in U.S. Pat. No. 6,250,820-B1.

1. A coupling arrangement for optically coupling a multi-channel optical plug-in element to at least one opto-electronic converter of a multi-channel transmitting or receiving unit, the coupling arrangement comprising: a coupling unit which comprises: a first coupling side for optical coupling to the multi-channel optical plug-in element, a second coupling side lying opposite the first coupling side for optical coupling to the at least one opto-electronic converter, and a multiplicity of high-precision through-bores for optical waveguides, said through-bores being arranged in a plane and extending from the first coupling side to the second coupling side in the interior of the coupling unit, wherein the coupling unit is of single-piece design, the coupling unit has, on its upper or lower side, a cut-out which partially exposes the through-bores for the optical waveguides in the interior, and the coupling arrangement furthermore comprises an additional auxiliary part which can be removed from the coupling arrangement and has a protruding knob configured for the coupling unit to be arranged on the auxiliary part in such a manner that the knob projects into the cut-out of the coupling unit and comes to rest adjacent to the through- bores for the optical waveguides.
 2. The coupling arrangement as claimed in claim 1, the coupling unit comprises two longitudinal bores for receiving and latching guide pins which each extend at the side of the through-bores for the optical waveguides, and the longitudinal bores each have, in an elastic wall region, a constriction which serves in each case for the latching of a guide pin.
 3. The coupling arrangement as claimed in claim 1, further comprising guide pins which are introduced into the longitudinal bores of the coupling unit and have an annular groove, the annular groove bearing in each case in the constriction of a longitudinal bore.
 4. The coupling arrangement of claim 1, wherein the first coupling side has the same basic dimensions as an end side of the optical plug-in element to be coupled, with through-bores of the optical plug-in element being aligned with the receiving openings through-bores of the coupling unit.
 5. The coupling arrangement of claim 1, wherein the second coupling side has a beveled projection exposing the receiving openings.
 6. The coupling arrangement of claim 1, wherein the coupling unit comprises a plastic shaped body.
 7. The coupling arrangement of claim 1, wherein the additional auxiliary part has a planar surface and a knob protruding from the planar surface.
 8. The coupling arrangement as claimed in claim 7, wherein the knob has an upper surface arranged parallel to the planar surface and two angled surfaces inclined in the direction of the planar surface.
 9. A method for inserting glass fibers into an optical coupling unit which comprises a single-piece design having a first coupling side, a second coupling side lying opposite the first coupling side and a plurality of high-precision through-bores for accommodating optical waveguides, which bores are arranged in a plane and extend in an interior of the coupling unit from the first coupling side to the second coupling side, comprising: a) providing a separate multi-channel optical plug-in element having receiving openings for optical waveguides, said openings being arranged in a plane, b) arranging the multi-channel optical plug-in element on the first coupling side of the coupling unit in such a manner that the receiving openings of the optical plug-in element are aligned with the through-bores of the coupling unit, c) inserting at least one optical waveguide initially into the optical plug-in element and continuing into the coupling unit, and d) bonding the optical waveguides in the through-bores of the coupling unit.
 10. The method as claimed in claim 9, wherein the coupling unit comprises, on its upper or lower side, a cut-out in which to place adhesive, the method further comprising placing the optical coupling unit onto an additional auxiliary part having a protruding knob during the insertion process in such a manner that the protruding knob projects into the cut-out and the optical waveguides to be inserted are prevented by the protruding knob from leaving the through-bores in the region of the cutout.
 11. The method as claimed in claim 9, wherein the multi-channel optical plug-in element comprises a standard MT ferrule.
 12. The method as claimed in claim 9, wherein the multi-channel optical plug-in element is removed after the optical waveguides have been bonded in the through-bores of the coupling unit.
 13. A coupling arrangement for optically coupling a multi-channel optical plug-in element to at least one opto-electronic converter of a multi-channel transmitting or receiving unit or to a multi-channel optical waveguide, the coupling arrangement comprising; a coupling unit which comprises: a first coupling side for optical coupling to the multi-channel optical plug-in element, a second coupling side lying opposite the first coupling side for optical coupling to the at least one opto-electronic converter or the multi-channel optical waveguide, and a multiplicity of high-precision through-bores for optical waveguides, said through-bores being arranged in a plane and extending from the first coupling side to the second coupling side in the interior of the coupling unit, wherein the coupling unit is of single-piece design, the coupling unit has, on its upper or lower side, a cut-out which partially exposes the through-bores for the optical waveguides in the interior, and the coupling arrangement furthermore comprises an additional auxiliary part which can be removed from the coupling arrangement and has a protruding knob configured for the coupling unit to be arranged on the auxiliary part in such a manner that the knob projects into the cut-out of the coupling unit and comes to rest adjacent to the through-bores for the optical waveguides. 